In recent years, it is a widely accepted practice to mount a switch for vehicles on the door portions of an automobile to detect the opening/closure of the doors and to control lighting in the compartment, such as turn on/off of light.
FIG. 4 is a sectional view of a conventional switch for vehicles. The switch for vehicles includes casing 1 made of an insulating resin of nearly a box-like shape with its upper surface opened, and operation body 2 made of an insulating resin. Operation body 2 is contained in casing 1 so as to move up and down, and is provided with operation portion 2A of nearly a cylindrical shape at an upper part of operation body 2.
Fixed contact 3 made of an electrically conducting metal is studded in the right inner side surface of casing 1, and terminal portion 3A of fixed contact 3 is protruding into nearly box-like connector portion 1A at the lower part of casing 1.
An end of mounting plate 4 made of an electrically conducting metal is anchored to casing 1. Mounting plate 4 is partly folded downward to form contact portion 4A, and through hole 4B is formed in the other end of mounting plate 4 that extends leftward and outward of casing 1.
Nearly U-shaped moving contact 5 made of a resilient metal plate is mounted at a central portion thereof on operation body 2, and the right and left ends of moving contact 5 are separately and resiliently contacted in a slightly deflected state to contact portion 4A and to fixed contact 3 of mounting plate 4.
Coil spring 6 is mounted in a slightly deflected state between the inner bottom surface of casing 1 and the lower surface of operation body 2. Operation body 2 is urged upward due to spring 6.
Cover 7 made of, for example, a rubber, has mounting plate 4 insert-molded therein, covers the upper surface of mounting plate 4, and has dome portion 7A thinly formed on the right side of cover 7, which is covering the upper surface of casing 1 and operation body 2.
Further, cylindrical portion 7B is formed on the upper side of through hole 4B in mounting plate 4 formed on the left side of cover 7, and insertion hole 7C of a diameter larger than through hole 4B is formed in the bottom surface of cylindrical portion 7B. Threaded portion 8A of metallic screw 8 is inserted in insertion hole 7C and in through hole 4B.
A plurality of protruded pawl portions 7D are formed on the inner side surface of cylindrical portion 7B of cover 7 to protrude inward beyond washer portion 8B of screw 8. Screw 8 is temporarily held in cylindrical portion 7B being prevented by pawl portions 7D from escaping upward. The switch for vehicles is thus constituted.
The thus constituted switch for vehicles is preserved or transited in a state where screw 8 is temporarily held in cylindrical portion 7B of cover 7. Terminal portion 3A protruding at a lower portion of casing 1 is connected by a lead wire (not shown) or the like to a lamp in the compartment through an electronic circuit (not shown) of an automobile. Screw 8 is fastened to the chassis (not shown) of the vehicle, and mounting plate 4 is grounded to the chassis via screw 8 and is attached to the door portion of the vehicle.
In a state where the doors of the automobile are closed, operation portion 2A covered by dome portion 7A of cover 7 is pushed by the door, operation body 2 moves downward while deflecting spring 6, the left end of moving contact 5 mounted on operation body 2 separates away from contact portion 4A of mounting plate 4, the connection between contact portion 4A and fixed contact 3 is broken, and the lamp in the compartment is turned off.
The door when it is opened separates away from operation portion 2A. Being urged by spring 6, therefore, operation body 2 moves upward. Contact point 5, too, moves up, returns back to the initial state of when turned on shown in FIG. 4, whereby the lamp turns on in the compartment to illuminate the interior of the compartment.
As prior art technical document information related to the invention of this application, there has been known, for example, Japanese Patent Unexamined Publication No. 2003-132761.
The switch for vehicles of the above prior art, however, has a constitution in which screw 8 is temporarily held in cylindrical portion 7B of cover 7 by protruded pawl portions 7D. Therefore, screw 8 may often escape in case shock is given thereto or a force is exerted from the lower side of the screw 8 while the switch is being transited or attached to the vehicle. If screw 8 happens to escape, screw 8 that has escaped must be inserted in cylindrical portion 7B again before tightening it, and a laborious work is required for the assembling which is inconvenient.